There are countless applications in which it is important to remove contaminants from water streams prior to further treatment or prior to discharge into sewers, waterways, and the like. Examples of materials which must be removed from such water streams include oil and grease emulsions, heavy metals, contaminants exhibiting basic oxygen demand (BOD), e.g., organic food particulates, and contaminants exhibiting chemical oxygen demand (COD), such as organic dyes, colloidal solid particulates, and agricultural organic contaminants. For example, the effluent from a typical commercial car wash or coin-operated laundry contains oil and grease emulsions, heavy metals, and colloidal solid particulates. Other process streams may include various other combinations of these and additional contaminants, in a relatively large volume of water. As these contaminants are normally dissolved or dissociated in the water stream--that is, as distinguished from being comparatively large particles--they are difficult to remove employing typical physical filtration steps.
The prior art teaches many process steps and techniques, many devices, and numerous combinations thereof for causing such particulates and other contaminants in a water stream to coagulate (including in this term "coalesce", "flocculate", "agglomerate", and other terms of like import) so that they can be removed by physical separation processes, typically including filtration. For example, it is known to add flocculants, coagulants, and the like to a process stream, again, to draw such contaminants out of solution and to agglomerate particles for filtration.
It is also known to mix oxidant gases and the like including ionized oxygen or allotropes thereof into waste water streams, specifically for coagulation of contaminants and the like for subsequent filtration. See U.S. Pat. No. 4,655,933 to one of the inventors hereof and another. U.S. Pat. No. 4,562,014 to one of the inventors hereof discloses a system for so doing involving a venturi for dispersing a gas into a liquid to be treated, encouraging mixing of the gas and the liquid due to the drop in pressure at the venturi.
It is also known to perform a variety of filtration steps downstream of a system for flocculating or coagulating pollutants in a water stream by passing the stream through an electrochemical filtration device. See U.S. Pat. No. 4,382,866 to one of the inventors hereof, and co-pending commonly assigned application Ser. No. 08/377,620, filed Jan. 25, 1995.
The art is also aware that many undesired materials to be removed from a water stream are typically polarized, such that a magnetic field in the water stream can be of use in causing such particles to agglomerate, coagulate, and/or coalesce for subsequent removal. However, the art has not provided a simple and efficient way of applying a magnetic field to such a stream of water to be treated.
Further, the art is aware that any coagulant to be mixed with a water stream to be purified must necessarily be thoroughly mixed with the water stream, so as to obtain maximum efficiency in its use. This is true whether the coagulant is an ionized gas, such as oxygen or nitrogen, or an anionic or cationic polymer liquid as often used for coagulant or flocculant purposes. However, the art does not teach fully satisfactory apparatus for thorough and complete mixing of coagulants, typically comprising ionized gases or liquids, with a stream of water to be treated thereby.